I just don't get it..some explain?

[. .]

Simple question. Your going into a busy airport. You have no idea how far down wind you will go. Remember fuel consumption at low altitude is much higher than at high altitude. Do you plan for a long down wind and start down slightly late and use spoiler if required? Or do you start down exactly as would normally be planned and risk powering up for an extended period of time, at low altitude, if given a long down wind?

What is the more efficient way to plan the arrival?

A lot of this is intuition and experience. There really isn't a right or wrong answer. The use of spoilers is a tool, not an indication of poor planning

This is what is so wonderful about Heathrow. Once you get handed to the arrival controller he gives you the exact track distance to the threshold which allows a planned idle descent. He has it all mapped out prior to the hand off. I find most major airports stick to a game plan unless the situation dictates otherwise allowing pilots to manage energy in the descent. I think the controller's best weapon is an efficiently designed arrival STAR and airlines are getting more involved in their design for that exact reason. Even with the engines at idle, the use of a speed brake is still consuming energy and does have an effect on fuel consumption.

Any speed other than your best L/D speed is also consuming more energy than flying best L/D. I think it's semantics to say that deploying speed brakes for 30sec is a big no no, but it's okay to run the speed up 20kts on the descent is okay. I think it would be a pretty safe bet to say that no one on here has the slightest clue about what the difference in burns between the two techniques would be, so it's silly to argue.

[AuxBatOn]

Any speed other than your best L/D speed is also consuming more energy than flying best L/D. I think it's semantics to say that deploying speed brakes for 30sec is a big no no, but it's okay to run the speed up 20kts on the descent is okay. I think it would be a pretty safe bet to say that no one on here has the slightest clue about what the difference in burns between the two techniques would be, so it's silly to argue.

I can tell you with great certainty that the drag generated by spoilers/speed brakes is generally greater than the drag created by a speed deviation from the L/D max. If you want, I can go back in my books and prove it (to be honest, I'd rather not, but I'll take the time and effort to do it if you so wish)

[complexintentions]

I have to totally disagree with the idea that using speedbrakes always implies some sort of error on the pilot's or ATC's part. Perhaps in a turboprop or light turbojet, but not in a heavy airliner. The wing on a modern medium-to-widebody is so efficient that if you are descending at idle and need a speed reduction or increased descent rate, the ONLY way it will happen is with speedbrakes. (Talking about descent phase here, not approach.) There is far more inertia in an aircraft weighing 240 tons than there is in one weighing 10 - speedbrakes are essential kit in managing energy.

If you're high on a descent profile, you can try to compensate by dialing the speed up on descent to increase the descent rate...but guess what, when you inevitably need to slow down, that speed reduction will cost you nearly exactly the same vertical profile you gained - it's basically a zero-sum game. So now you're on speed...but still high. Out come the brakes to get down. Choose your poison. I prefer to speed up when high, when altitude/ATC/turb allows, as it prevents the buffeting of the speedbrakes for the pax, but that's purely technique, not any attempt to save fuel.

The only way you could avoid use of drag devices 100% of the time would be to either know exactly what your track miles to run are (like in LHR, as mentioned) or on a closed STAR, or to start down so early you're under the profile all the way in...hardly efficient.

As far as speedbrakes vs. spoilers, it strikes me as a pedantic discussion. Various panels on the wing at various times act as spoilerons in slow flight, speedbrakes in airborne phases, and spoilers on the landing roll. How much of the energy is shed due to drag vs. how much is lost due to the spoiling of lift, I dinna care...I just wanna slow the beast down!

[Idle Thrust]

Spot on complexintentions, best post yet.

The DC-8 was a nice airplane but its lack of speedbrakes was a real pain. Descending into any busy terminal area, especially in the U.S. was a challenge because virtually every other jet had speebrakes and ATC wanted you to follow their profile, the only recourse was reverse thrust which most of us abhorred (in the -73 series you would swear you just had a mid-air). So what you had was a "missing tool", one which I many times wished that we had.

And for AuxBatOn, those panels on the upper wind surface are multi-taskers - roll control spoilers, landing rollout lift dumpers, speedbrakes, the L-1011 even used them as "direct lift control" devices. It's all a matter of terminology, end result is the same. Methinks your technical knowledge far exceeds your practical experience piloting large jet airplanes.

Edited to correct DC-8 series (-73F vs -63)

[tonysoprano]

I gotta say this is one of the most ridiculous threads I've ever seen particularly the initial one. But great to see everyone is being a good sport. As for the speedbrake/spoiler thing...

) using the speed brakes during the desecent( arent pilots taught to manage speed and not use the brakes, used then both ways, im havent starteded my flight training yet, soon so im not 100% sure) i mean the pilots of both of my flights used the speed brake over 50% of descent.

In the air, speedbrakes (spoilers/airbrakes, whatever) are there to be used as required. It's not because you've done something wrong necessarily and you are no less of a pilot for using them. The airplane sometimes just does not do a good job flying required descent profiles (speed and alt) at busy airports. Sometimes you have to intervene and one way is to use speedbrakes. They CAN be used to slow down but more often are used to increase rate of descent to make a certain alt and speed restriction. Someone has suggested they are a fuel guzzler. Not quite. On airplanes with autothrust, the thrust is usually commanded to the idle position or near it. Yes and BTW, no matter what you call them, they are used to accomplish the same thing. Complex, I should have read your post first, would have saved some time by not posting myself. You're bang on with a good summery.

[AuxBatOn]

It's not because you've done something wrong necessarily and you are no less of a pilot for using them.

I said it may be a cause of why you use them. Obviously, there are other reasons. All I'm saying is if you can avoid using them, do so!

Someone has suggested they are a fuel guzzler. Not quite. On airplanes with autothrust, the thrust is usually commanded to the idle position or near it.

Agreed, however, by not planning on using the speed brakes/spoilers, you can start your descent X minutes earlier (and still achieve a speed/altitude restriction), thus reducing your time at higher power setting in cruise. That's what I meant by "throwing buckets of fuel out the window". Obviously, again, depending on wether it is possible to descend earlier or not.

Yes and BTW, no matter what you call them, they are used to accomplish the same thing.

Yup, from a pilot's perspective it's all the same. I'm, however, a firm believer that a pilot should know his aircraft's systems, at least the basics. Personally, I like puting a lot of toughts in what I do, and I spend countless hours trying to figure stuff out (which may seem for most people a waste of time, but to each his own I guess!)

Spoilers increase stall speed, while speed brakes usually don't. I believe that fact contributed to AC621's accident at Pearson in the 70s, when the F/O deployed the spoilers in the flare.

Methinks your technical knowledge far exceeds your practical experience piloting large jet airplanes.

Yup, you're right, my experience with large jets is nil, and I have done studies in the subject. So you can say that my technical knowledge exceeds my experience in the matter. But I do fly a small, slick jet (that doesn't want to slow down), in which it can be difficult sometimes to manage your energy. And I try to avoid using speedbrake. Obviously, when it is not possible, I use it... And try to avoid getting in the same situation again.

[tonysoprano]

Yup, from a pilot's perspective it's all the same. I'm, however, a firm believer that a pilot should know his aircraft's systems, at least the basics. Personally, I like puting a lot of toughts in what I do, and I spend countless hours trying to figure stuff out (which may seem for most people a waste of time, but to each his own I guess!)

From a pilot's perspective? How bout from Boeing's perspective. The AOM calls them "Speed Brakes". Period. Maybe that's because that's what they are. Or perhaps more importantly because from a pilot's point of view, we don't need to know more than that. Sure that's only Boeing. But that's what I fly so that's all I need to know. Catch my drift? If you want to pretend you're flying the space shuttle, that's your decision.

Yup, you're right, my experience with large jets is nil, and I have done studies in the subject.

Right. I'm outta here.

[whipline]

First off, using speedbrakes/spoilers is up to the pilot, if you want to use them fill you boots. But you should know what you are doing, why your doing it and other ways of accomplishing the same task.

Aux your right again, its not the size of the jet its the design and the weight.

Jaques, good post. If I was unfamiliar with the airport I would pull out the breifing, ask my colleague, look at the arrival/approach, if possible ask ATC what to expect, ask for directs and for the first arrival for both of us plan to be slightly low to avoid a vector or a go-around.

Complexe, nice post by I disagree. If your in the mid 30's or higher, you can go by your top of descent point by 4000-6000 feet and make 250 at 10,000. This of course is assuming you were not planning on descending at or near you mmo/vmo and obviously type and weight of aircraft. If your restricted in speed then yes the only way to increase rate would be the spoilers/speedbrake. For me thats why they are there.

Endless, you understand the difference but here is a simple thought. If you saved 50 dollars in gas every flight, did 4 legs a day and flew 15 days a month thats around 35,000 a year. Times that by 1000 pilots in your company. Its the same principle as doing single engine taxi, using ground air/power instead of the APU, reducing the amount of drink and food, paperless cockpits, noise abatement 2 instead of 1, staying clean on approach as long as possible. It might not seem like much but in the end it really adds up. If your pulling the speedbrake/spoiler simply because the FMC/MCDU told you to, your most likely wasting money.

[Rockie]

Nothing like getting lectured on the difference between speedbrakes and spoilers, or reminded that we should always be planning a perfect idle descent so we don't have to use them. In Bumf**k Saskatchewan that might actually work where there are no other airplanes to worry about. However here in the real world it's a little more dynamic and the speedbrakes (or spoilers if you prefer) are a tool to be used when required.

Auxbaton

You have a 10,000 ft restriction to make at WASIE and are executing your perfect idle descent at 300 kts when ATC tells you to slow to 270 for spacing. Not his fault and not yours. How would you handle it without hanging your head in shame?

[AuxBatOn]

Rockie, I'll go back to my very 1st post in this thread :

I don't know... IMHO, using speed brakes is the same as dumping buckets of fuel out the window. Unless you absolutely need it (most likely because someone screwed up, ATC or pilot, or for other ops restrictions from ATC), don't use it. There are other ways to control speed during the descent. May not be a player on severe clear days, but if you need to divert, you may wish you had that extra XXX lbs of fuel the speedbrakes took away from you.

[Jaques Strappe]

I said it may be a cause of why you use them. Obviously, there are other reasons. All I'm saying is if you can avoid using them, do so!

Exactly! I think everyone is talking circles around the same answer. Obviously if you are descending on profile at idle and get an unexpected 50 knot speed restriction ( which seems to inherently occur at some airports more than others ) you will probably need to use them for a short term. That being said, I don't know how many guys I have seen who automatically reach for them even when there is still room to bleed the energy by simply raising the nose a little. Or use them at high altitude when there is still loads of room to get back on profile. Even worse, I have seen guys automatically pull them out when given a speed reduction only to have the auto thrust bump up in an attempt to stay on profile. Descending with speed brakes deployed and the thrust working it's way north of 50% with guys totally oblivious. Call it a pet peeve but it really annoys me.

In the Embraer which uses only a defined flight path angle to compute descents, I see guys totally give up and just descend with the thrust on, probably at least 80% of the time in fact. That would be an automatic S/B during a line check on the DC9 where the profile was computed in the pilots head due to no FMS or even a GS readout but today, even with all the available information, there is an issue with people " over using " the speed brake because it is there and it is easy.

[Brick Head]

Auxbaton and whipline,

Endless, complexintentions, tony are all bang on.

What appears to come through your postings is the idea that speed increase is somehow an efficient way to shed energy. More efficient that other methods. I would suggest you think of this from a purely potential energy prospective. It doesn't matter how you in efficiently shed it. What matters is that you did.

Auxbaton wrote

I can tell you with great certainty that the drag generated by spoilers/speed brakes is generally greater than the drag created by a speed deviation from the L/D max. If you want, I can go back in my books and prove it (to be honest, I'd rather not, but I'll take the time and effort to do it if you so wish)

Exactly. Which is why the speed increase is needed longer than spoiler use. The gear would be even faster. In the end it does not matter what form of drag you use to shed a specific amount of potential energy. Get rid of 4000 feet with spoilers/get rid of 4000' with speed increase. All the same. You just inefficiently shedded 4000 feet of potential energy.

Whipline wrote:

Aux your right again, its not the size of the jet its the design and the weight.

Partly the design. But it is all about the weight. I can tell you right now, what you think won't slow down today, will seem like it had a brake pedal on it a few years from now.

Whipline wrote:

Complexe, nice post by I disagree. If your in the mid 30's or higher, you can go by your top of descent point by 4000-6000 feet and make 250 at 10,000.

Again semantics. It doesn't matter how you shed the extra potential energy (4000-6000 feet). What matters is that you did it. Inefficiently shedding 4000-6000 feet of potential energy is the same thing no matter what form of drag you use. By the way I'm thinking that would be one light aircraft.

Whipline wrote:

Endless, you understand the difference but here is a simple thought. If you saved 50 dollars in gas every flight, did 4 legs a day and flew 15 days a month thats around 35,000 a year. Times that by 1000 pilots in your company. Its the same principle as doing single engine taxi, using ground air/power instead of the APU, reducing the amount of drink and food, paperless cockpits, noise abatement 2 instead of 1, staying clean on approach as long as possible. It might not seem like much but in the end it really adds up. If your pulling the speedbrake/spoiler simply because the FMC/MCDU told you to, your most likely wasting money.

Your absolutely right. I don't think endless or anyone here would disagree with you. Plan efficiently. Idle all the way down at the correct target speed. What you are getting is response to the idea that increasing speed is somehow a more cost effective way to shed potential energy than spoiler use. This whole concept, that some ways of expending potential energy, are more efficient than others is completely misguided.

[tailgunner]

I might add that speedbrake/spoiler use is often predicated on what the traffic in front of you is doing. Different airlines with different aircraft types often dictate the way one can plan a descent. We plan and transition at 290 kias, but the boeing boys have slowed their transition speeds to 265kias I think. The MD's in the US transition at 300 or better, so they really chew us up.

[tonysoprano]

tailgunner, good point. Just be careful which boeing you refer to.

I'm stating the obvious here: You use extra speed or speed brakes or a combination. I think we are all saying the same thing but the "intellectuals" are just trying to show off as usual. Yup, the college kids have arrived. Thank God we just follow our SOPs and experience and not the rocket scientist theories. On paper, they are geniuses. In the real world, I'll take experience to accommodate ATC, my airplane and the prevailing conditions. The rocket scientist theory never and I mean never takes into account two things: ATC and environmental conditions, aka "the real world". ATC can speed you up, slow you down and have you going around in circles. Environmental conditions such as ice, turbulence, weather, wind changes etc can all affect the efficiency of the theories that sound so good. Scientists and curious minds are labour intensive pilots. I haven't said anything that you guys didn't already know. But the rocket scientists have to take it to another level as always to prove they were good in school. At the end of the day, your penny pinching theories are not "make it or brake it innovations". You "brainees" are a wasting your time. There's something bigger than you out there but you haven't figured it out yet. Or maybe you have but you still feel the need to show off your useless intellectual "power".

[Donald]

Just give the "intellectuals" a runway change, then stand back and smell the smoke curling up from the ol' cranium.

[complexintentions]

@Jacques

Obviously if you are descending on profile at idle and get an unexpected 50 knot speed restriction ( which seems to inherently occur at some airports more than others )

*cough*Pearson*cough* Couldn't resist, yep I noticed it!

Descending with speed brakes deployed and the thrust working it's way north of 50% with guys totally oblivious.

Just curious, does this config not set off any alarms in the Emb? Post-Cali, the Boeing will give a master caution if the autothrust comes up with speedbrake up.

@Whipline

Complexe, nice post by I disagree. If your in the mid 30's or higher, you can go by your top of descent point by 4000-6000 feet and make 250 at 10,000. This of course is assuming you were not planning on descending at or near you mmo/vmo and obviously type and weight of aircraft.

Sorry, but it really comes down to type and weight. On the B777 you simply can't shed 4000-6000 feet and make 250 at 10 with airspeed alone. I know you can on a -37 or a bizjet. But with something really heavy you have to drive it at Mmo so far below the profile for the speed reduction that it becomes impractical. If they've left you that high it's generally for other reasons like they're gonna hold you so it's a bit of a non-scenario. If that DOES happen we would generally try and regain as much profile as possible by trading speed and then the rest with the speedbrakes. Most ATC units will just vector you for more track miles if it's really that excessive.

@Tony

hey man, not too hard on the college kids! I freely admit there are many younger, smarter guys out there who know far more than me about the theory of lift/drag, and I'm cool with that...but when they start to spread information that is just plain wrong, which is then eaten up by others who also don't have the experience to know better, I am inclined to jump in with my two hard-earned bits.

[iwannasoar]

i have some ideas for aircanada to save costs. i was amazed how much time/fuel they wasted on a short hop from Toronto-Ottawa, then on my return trip back to yyz.

1) what the heck is the point of stuffing the plane w/ pop,beer,liquor, food for a 45 min flight to ottawa (cyow) from YYZ, i mean for all that extra weight on board the airplane dosent make sense, im a 18 yrs old and i can go an hour without food, or a pop. i was amazied to see the food cart stuffed with crap for a 45 minute flight. the majority of people on shorts hops like these are business men that could care less about anything but there blackberry.

4) PTV's in every seat? for a 45 mins flight ? I know planes are often used on different routes, but they should really change that for these short hops, they make tons of these trips daily, why not have a Aircraft dedicated to it?. the added weight has to be underrated. ohh and why have 100 copies of the damn toronto star, (and others..) have a stand in the gate, with the paper, you want one take one. but paper weighs alot, and probably adds a good 50-70 lbs.)

when you make non-stop trips like these, the cost adds up they could potentially save the company huge amounts of money. I don't know, i know i wouldnt miss the crappy food, the pop and eventually the 6 dollar beer. would you?

anyone wanna explain to me? am i wrong? i would like to here some input
end of rant.
ps, i wrote this quick on my buddy's laptop im not used to, if i made a few mistake, sorry)

I'll take this another direction. I had a look at a YYZ-YOW flightplan last night and the fuel penalty to take an extra 1000kg over flightplan was 38kg of fuel. It was a A321 with about 174 pax seats.
Broken down to have all those newspapers, pop, beer, snacks etc on board (assuming that it all weights in at 1000kg) it works out to about .21/seat assuming about a dollar a litre for the jet fuel. I think that these are all small creature comforts that have become expected on flight and the actual costs are quite minimal. I guess if you do want to same some pennies there is always Aeroflot and Greyhound.

Also I was at Milestone's for dinner last night and I paid $7.00/beer. The waitress was only marginally better looking that the average "Sky witch". All in all it does not seem too out of line to me

[CCR]

Tailgunner,
you mean we have "sped up to 265kts"!! New CI's the last 6 months with fuel cost diving so we are no longer doing 249-256!!

[Old fella]

O/K Captains and F/O's. I think we got the message and your various thinking. From a pax prospective we don't really care what you use to slow down(throw out your dicks and the FA's drawers if it will help - we don't care) or speed up or whatever ATS has you do. Just get to our destinations on time as humanly possible, keep her right side up and hopefully our baggage will arrive on the same flight(although you have nil control over that).

......... and WJ, make sure you have some Keith's Red on board as I am heading down south to sun thy arses within a few weeks on one of your flights

[Jastapilot]

Keith's Red? Is that a Cabernet?

[tonysoprano]

....it is on WJ.

[Jaques Strappe]

Complex

Just curious, does this config not set off any alarms in the Emb? Post-Cali, the Boeing will give a master caution if the autothrust comes up with speedbrake up.

The airplane is not that sophisticated.

[Brick Head]

Complex

Just curious, does this config not set off any alarms in the Emb? Post-Cali, the Boeing will give a master caution if the autothrust comes up with speedbrake up.

The airplane is not that sophisticated.

If any of these things happen with the spoilers extended, the spoilers will retract, you get a spoiler disagree message and the wing picture pops up on the status page and shows an amber spoiler.

180kts or less
flap 2
thrust above XX. Can't remember the number. Must be above 50% n1 though.

To regain the spoilers you must select the spoilers back to up. Then redeploy them. This one is new. Don't know with what load but I know it wasn't always this way. I remember an FO doing a GA from the FAF, unstable, in the sim with the auto thrust off (yeah auto throttles). When he pulled back the thrust the spoilers redeployed. He crammed the power back up and and they retracted. Repeat at least twice.

The cali scenario would not happen on the emj. The spoilers would auto retract and let you know with a spoiler disagree message.

Anyway went into LAX last week. High, flap 1, assigned 180kts. Tripped the 180kts retraction limit. Spoilers would not work once speed above 180kts. Had to retract then redeploy. Did it twice to make sure.

Jaques. I'm starting to believe they do stuff between loads they don't tell us about.

That was a joke. you and I maybe the only ones who get it.

[Old fella]

....it is on WJ.

Somebody told me WJ is a "beer quaffing" airline especially on those AT charters they do to southern destinations from the maritimes. At least in a B737-800 ya can unload a jug or two of Keith's(which I intend to quaff at CYHZ with the other lads/lassies of the bunch) unlike, say Tony, your connector airline that has that certain twin jet built in Canada with 50X4.

[complexintentions]

Hey MURRAY, I hear if you say something enough times, it makes it true! lol

Points to ponder:

-I hate paxing through LHR. But I'm pretty sure YYZ would do no better if they were trying to process about 40 million more pax than the place was designed for. I'd still rather operate into LHR over YYZ any day of the year. The controllers just seem more professional. Maybe it's the British accents?
-I'd way rather hold at LAM for 8 minutes and be given a precise EAT followed by a constant descent angle approach to landing than multiple large speed changes, level-offs, and runway switches.
-Toronto is an ok city, but London is well...LONDON! 'Nuff said.
-This thread has absolutely sweet F all to do with your Quixotic defense of the GTAA.

toodle-pip and cheerio and all that!